Currently, the primary cathode material for lithium ion batteries used in cell phone and laptop computers is LiCoO2. LiCoO2 shows original discharge capacity of 140-145 mAh/g and has good cycling characteristics and has been used extensively for cathodes in lithium ion batteries. However, LiCoO2 is expensive because of the shortage of Co. At the same time, LiCoO2 has low capacity and is unsafe. In recent years, extensive research was conducted on preparation of lithium manganate (LiMn2O4), LiNiO2 and other materials to formulate low-cost high-performance cathode materials. Application of LiMn2O4 is limited to small electrokinetic cells due to its low charge capacity and inferior cycling performance, especially under high temperatures. Application of LiNiO2 is limited to experimental research because of difficulties in synthesis.
LiNiO2, LiCoO2, LiMn2O4 multi-element cathode material (MCM hereafter) is a new material for high-capacity lithium ion battery cathode. It has excellent safety properties, relatively low price, good compatibility with electrolyte and outstanding cycling performance. However, the application of this material is limited because it is difficult to synthesize, is relatively unstable and has lower density than LiCoO2. In recent years, preparation of MCM improved significantly. Compound crystal particles of MCM, mostly spherical-like, were prepared and it was shown that each particle is an aggregate or combination of multiple particulates. The tap density of such material could reach 2.0˜2.5 g/cm3, and the initial discharge capacity could reach 140˜145 mAh/g. At present, MCM produced in trial-production by cathode material producers are of the compound crystal particle type. This type of material requires complicated preparation technology, and although it has relatively high tap density and its compacted density could reach 3.2˜3.4 g/cm3, there is limited room for increasing its density. In addition, because it is difficult to achieve uniformity of the sizes among the compound crystal particles that are made of particulates, there is a wide distribution of granularity, resulting in particulates falling off the surface of compound crystals, which is detrimental to the stability of the products. Furthermore, spherical-like compound crystal particles show increased hygroscopicity that negatively affects the service performance of the products.